Wireless communication networks, such as wireless wide-area network or wireless local-area networks (WLAN) such as IEEE 802.11 wireless communication networks are able to provide communications for their mobile subscriber units (MSU) utilizing wireless access support through local access points (AP). One task that any MSU typically deals with is an ongoing evaluation of the radio frequency (RF) environment. The MSU, for example, can evaluate the RF environment with the AP for adjusting transmitter operations, or consider the information in its roaming, and scanning algorithms.
There are multiple methodologies in use for RF link evaluation. However, they all have one or more of the following conceptual deficiencies. Firstly, the local MSU antenna can physically perceive the RF environment at only discrete events of transmitting or receiving WLAN traffic. For example, signal strength indicators are provided as discrete power measures that can be subjected to the way the MSU is held and antenna-sensitivity at each moment, which would not always mean that the RF environment really changes. In another example, there can be some discrete points in time where a connection is lost due to local aspects and positioning of the MSU.
Secondly, a number of WLAN protocols facilitate information exchange between the MSU and APs with regards to RF status. For example, IEEE 802.11k can inform the MSU with Radio Resource Measurements data, which is compiled to reflect RF utilization, load, capacity, noise, interference, etc. This data is very helpful for an MSU's scanning and roaming decisions. However, producing this information requires active messaging between the MSU and AP, and is not under the control of the MSU. In addition, this active messaging is not trivial to synchronize, and could be interruptive when there is an active voice or video session over the WLAN link.
Another task that any MSU typically deals with is operating in a power saving mode wherein the transmitter, and optionally the receiver, is powered down during predetermined time periods. The power saving mode is intended to meet three major objectives: 1) conserve as much battery power as possible. That is, maintain a scheme that would turn the radio off when it is not used, as oppose to have the radio being continuously awake, 2) provide a stable wireless connection with the network as the MSU roams around, and 3) keeping the MSU receiver on when expecting to receive data from an AP.
Once an MSU completes negotiating a Power Save (PS) scheme applicable with the network, and establishes the successful connection, the MSU then configures its receiver to match predicted performance with the network protocol properties, after which the PS scheme remains static for the duration of the connection. However, this scheme has two problems. First the PS negotiated scheme does not provide information about the environmental Radio Frequency (RF) situation at the time of the connection, which may not fit the RF environment optimally. Second, even if matching could be better optimized at the time of the connection, environmental RF factors do change over time.
It is noted here that while some existing MSU implementations do apply dynamic adjustments per environmental changes to improve their performance, they do so by adjusting the transmitter only, and not the power save characteristics of the receiver. However, receivers have not been adjusted when subjected to RF issues, which has a large impact on the stability of the connection and the incoming traffic.
Accordingly, there is a need for a new technique to adapt a power saving mode for a receiver of a mobile subscriber unit in a wireless communication network in response to changing RF conditions.
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